Re: log_archive_max_processes in DG

From: Ravi Madabhushanam <ravi.madabhushanam_at_gmail.com>
Date: Fri, 3 Jul 2009 13:05:07 +0530
Message-ID: <f2f282d10907030035m3982192ci73533d255ded709a_at_mail.gmail.com>

Kumar,

IMHO , setting LOG_ARCHIVE_MAX_PROCESSES to 30 would be an overkill. General setting would be 4 to 6. I recommend setting this value as per your present environment and DG configurations.

This parameter can be modified using "alter system" .

You need to consider the below aspects when setting this parameter:

1. peek Redo generation rate
2. Size of REDO log file
3. Datagaurd mode ( LGWR or ARCH) if it is LGWR then

log_arch_max_processes will not play significant role. 4. Network latency for standby

If the redo log size is more and network latency is also on the higher side i would recommend having this value to number of redo groups to make sure that there is always one spare archiver process to address local archiving, in case all other are busy in archiving remote destinations.

Regards,
Ravi.M

On Thu, Jul 2, 2009 at 9:51 PM, Kumar Madduri<ksmadduri_at_gmail.com> wrote:
> Hi
> I have seen several examples of Data Guard setup where
> log_archive_max_processes is set at 30. But I read that setting these to
> high values can cause memory issues. Oracle documentation on this parameter
> also says the default of 2 should be fine for most cases. What should this
> number be set when you are setting up Data Guard?
>
>
> The LOG_ARCHIVE_MAX_PROCESSES initialization parameter specifies the number
> of ARCn processes that the database initially invokes. The default is two
> processes. There is usually no need specify this initialization parameter or
> to change its default value, because the database starts additional archiver
> processes (ARCn) as needed to ensure that the automatic processing of filled
> redo log files does not fall behind.
>
> However, to avoid any runtime overhead of invoking additional ARCn
> processes, you can set the LOG_ARCHIVE_MAX_PROCESSES initialization
> parameter to specify up to ten ARCn processes to be started at instance
> startup. The LOG_ARCHIVE_MAX_PROCESSES parameter is dynamic, and can be
> changed using the ALTER SYSTEM statement. The database must be mounted but
> not open. The following statement increases (or decreases) the number of
> ARCn processes currently running:
>
> ALTER SYSTEM SET LOG_ARCHIVE_MAX_PROCESSES=3;
>
>
> Also another related question is about Standby Redo Logs. If you are
> planning to set the DG in max performance mode, would there be any advantage
> in adding SRL? I undertand that having SRL will give the ability to have the
> lates online redo log info in SRL and decreases my recovery time. But if
> that is not a criteria , would I be better off without adding SRL (From a
> performancce point of view).
>
> Thank you
> - Kumar
>

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Received on Fri Jul 03 2009 - 02:35:07 CDT